1. Field of the Invention
This invention relates to a collapsible rubber dam installation comprising a rubber dam built across a watercourse such as a river or the like and operative to be raised by supplying fluid such as air, water or the like thereinto and to be collapsed by discharging the fluid filled therein to atmosphere.
2. Description of the Prior Art
Collapsible rubber dam installations have been applied to agricultural water taking dams, rising tide preventive dam, sea water obstructing dam or the like. Heretofore, it has been the common practice to supply fluid into a collapsible rubber dam to raise it and discharge the fluid filled therein into atmosphere to collapse it by means of a pipe line installation composed of a horizontal pipe embedded in a riverbed on which is disposed the rubber dam and a plurality of branch pipes for connecting the horizontal pipe to the rubber dam. In addition, a fluid suction and exhaust device such as a pump, an exhaust opening or the like connected to the horizontal pipe are arranged in a control room located at one of river banks.
In such conventional collapsible rubber dam installation, fluid is supplied under pressure through the horizontal pipe and branch pipes into the rubber dam by means of a pump or the like for the purpose of raising the rubber dam. In this case, the water content contained in the fluid supplied under pressure is condensed into drainage which is collected in the rubber dam and pipe lines. Particularly, the drain is collected in the horizontal pipe embedded in the riverbed. As a result, in order to collapse the rubber dam by discharging fluid filled therein into atmosphere, it is necessary to open a first valve connected to the horizontal pipe for the purpose of extracting the drain collected therein and then to open a second valve connected through a vertical pipe to the first valve for the purpose of extracting the fluid filled in the rubber dam. Thus, a conventional collapsible rubber dam installation has the disadvantage that it is difficult to inflate and collapse the rubber dam and that such rubber dam inflating and collapsing operation is not efficient.
In addition, in case of emergency where the amount of flow of the river water becomes abnormally increased due to a flood or the like, it is usual to automatically open a float valve to discharge fluid filled in the rubber dam into atmosphere and hence automatically collapse the rubber dam. In this case, the conventional rubber dam installation provides the important drawback that it is impossible to discharge the fluid filled in the rubber dam owing to the presence of the drain produced by the condensation phenomenon and collected in the pipe lines. As a result, the rubber dam could not be collapsed.